The present invention relates to a catamenial pad or tampon or a diaper containing carboxymethyl alginate (CMA) and alginic acid salt.
Particular characteristics of a pad or a diaper made of fabrics from carboxymethyl alginate and alginic acid salt fibers are high absorbency and water-retentivity.
Natural materials such as cotton, pulp, and sponges made of synthesized polymers have been used as the absorption materials for a long time. Absorbing mechanisms are known as water-absorbing through capillary action. The absorbency is about 20 times, but water-retentivity is reduced since the absorbed water may be removed easily under external stress.
In order to solve the aforementioned disadvantages and to provide a material having very high absorbency and water retentivity, there have been many proposed types of synthetic polymers. Generally, these polymers have a hundred times of its own weight in absorbency.
These polymers also have high water retentivity even under a tolerable degree of stress. These materials may be used in the field of sanitary products, agriculture, gardening and architecture, and many other attempts have been made to expand the usage ever since.
Water absorbable resin was first developed by the United States Department of Agriculture Research Laboratories in the 1960's. The resin was prepared by hydrolysis after copolymerization of starch with acrylonitrile. Using the above method, Henkel Corp. and Grain Processing Corp. (U.S. Corporations) began to produce the resin commercially in the late 1960's.
On the other hand, Sanyo Chemical Co., Ltd. (Japanese Corporation) succeeded in developing highly absorbent material by graft polymerization of acrylic acid with starch. Many other manufacturers have developed highly absorbent material from polyacrylic acid, polyvinyl alcohol (PVA), etc. In 1978, several manufacturers including Sanyo Chemical Co., Ltd. started pilot production of the material and in late 1978, sanitary products made of these highly absorbent materials appeared in the market. Thereafter, researches and experiments in this field were continuously carried out, leading to the development of the first paper pad made of this highly absorbent material. Later on, a paper diaper made of this material was developed.
Typically, these highly absorbent materials are supplied in two different forms. One is in the form of powder and the other is in the form of fiber. For example, the high absorbency resins in powder form may be taken from crosslinked compounds of polyacrylic acid salt, a graft copolymer of starch-acrylic salt (GSA) crosslinked compounds of PVA, and PVA/polyacrylic acid salt. The resins in fiber form may be taken from hydrolyzed polyacrylonitrile and crosslinked carboxymethyl cellulose (CMC). However, resins in the form of powder are difficult to process while resins in the form of fiber are easy to process and expensive but the absorbency is not as comparable.
In order to be used as sanitary products, a resin must have sufficient functions such as absorbency, water-retentivity, processability, and stability. The commercial sanitary products made of GSA or polyacrylamido sulfonic acid (PAAS) show relatively high absorbency in pure water. However, absorbency is reduced significantly to one tenth in salt solution.
Furthermore, processability of the resins in the form of powder are quite limited and can cause a pollution problem because of non bio-degradability. Although PVA/polyacrylic acid salt copolymer resin or starch-acrylic acid resin in the form of powder has sufficient gel-strength and thermal stability, these resins also have limited processability and have no bio-degradability.
Resins, like crosslinked CMC and hydrolyzed acrylonitrile can be spun into fiber and therefore processability is much better. However, absorbency is relatively low and the cost is 2-3 times more expensive than the resin in powder form.